Process for preparing a stable, freeflowing dishwashing composition



United States No Drawing. Filed May 24, 1963, Ser. No. 282,885 4 Claims. (Ci. 252-99) The present invention relates to novel washing and sanitizing compositions and to novel processes for preparing these compositions. The present invention more particularly relates to novel stable, free-flowing washing and sanitizing compositions which are suitable for washing dishes and which are especially useful in dishwashing operations, particularly in operations involving the use of automatic dishwashing machines, of the type designed for home use.

Aside from the mechanical desi n and construction of the dishwashing machine itself, one of the most important factors in the washing and sanitizing of dishes in automatic dishwashing machines is the selection of the washing or sanitizing composition. Such compositions must meet several requirements, the mostimportant of which is that a composition, when dissolved in water, will effectively remove dirt, food particles and other organic matter so that the dishware will be visibly clean and the dishwarewill be effectively ster lized on completion of the washing operation.

A second requirement of the washing composition is that it be non-corrosive when dissolved in water. Not only should it be non-corrosive to the various metallic components of the machine and to metalware that is washed in the machine, but it should also have a minimum or (andpreferably) substantially no, adverse effect upon the colored decorative glazes normally found on domestic ceramic or plastic dinnerware.

Another requirement of a satisfactory composition is that it should be readily soluble in water and at the same time have a bulk density of 0.5 gram per cubic centimeter or greater. The bulk density of the composition is particularly important since automatic dishwashing machines have been designed to operate and toclean dishes ethciently when compositions having a bulk density above 0.5 gram, usually above 0.6 gram, per cubic centimeter are employed in the dispensers used in such machines.

A number of washing and sanitizing compositions have been proposedheretofore for use in automatic dishwashing machines. However, these compositions possess the disadvantage of not meeting, or not fully meeting, one or more of the requirements (e.g. cleansing, sanitizing, noncorrosion), hereinbefore defined. The previously known compositions consist of mixtures of various inorganic salts such as alkali metal phosphates including trisodium phosphate, tetrasodium pyrophosphate and sodium tripolyphosphate and other salts such as sodium silicate, sodium chloride and sodium sulfate. Sodium chloride and sodium sulfate are employed to increase the bulk density of such dishwashing compositions, although the use of these materials tends to adversely affect the cleaning efficiency thereof. These previously known compositions often possess certain disadvantages in that they either lack suflicient cleansing properties, i.e., the ability to remove dirt and food particles when dissolved in water, and/or do not sanitize dishware against the possibility of bacterial growth after the dishware has been washed. Moreover, such compositions, when prepared under dry conditions and employing "anhydrous inorganic salts, often have an adverse effect upon the metallic components of automatic dishwashing machines and upon the aforementioned decorative glazes found on dinnerware.

Other previously known dishwashing compositions have consisted of mixtures of three or more of the above-mentioned ingredients and, such mixtures have included, in addition, available chlorine-containing materials such as chlorinated trisodium phosphate, trichlorocyanuric acid, and dichlorocyanuric acid, and certain nonionic organic surface active agents. Although. such compositions cleanse and sanitize dishware, if employed when freshly prepared, they are generally unstable on standing and tend to rapidly lose available chlorine and their sanitizing properties unless they are manufactured under substantially water-free conditions using the aforementioned inorganic salts in anhydrous form. As noted above, when anhydrous inorganic salts are employed, the compositions, when used, often have an adverse effect on the metallic components of automatic dishwashing machines and upon the decorative colored glazes of dinnerware. On the other hand, when these compositions contain moisture they are usually unstable with respect to loss of available chlorine and lose their ability to efiiciently cleanse and sanitize dishware.

It is one object of the present invention to provide novel, washing and sanitizing compositions which are particularly useful in dishwashing operations in which automatic dishwashing machines are employed.

It is another object of this invention to provide novel processes for preparing such novel compositions.

It is a further object of this invention to provide novel stable compositions comprising a hereinafter defined mixture of certain inorganic salts and sanitizing agents which overcome or materially minimize the aforementioned disadvantages of previously known compositions.

Other objects and advantages of the present invention are contained in or'will become apparent from the following description and appended claims.

The present invention provides stable, dry, free-flowing compositions comprising an intimate mixture of ((A) solid particles (hereinafter called phosphate species) in which the particles comprise a mixture of (1) a hydrated alkali metal tripolyphosphate, (2) an anhydrous to partially hydrated alkali metal silicate, and from about 10% to about 25% by weight of water in the form of water of hydration in the tripolyphosphate and the silicate, and (B) from about 0.5% to about 3.0%-

by weight, based on the weight of composition of solid particles (hereinafter called chlorine species) of an available chlorine containing compound in which the particles have a certain hereinafter defined particle size.

Such compositions are characterized in being readily soluble in water and in having a bulk density of at least 0.6 gram per cubic centimeter. Although such compositions may contain as much as 25% water, as water hydration, they are dry, free-flowing compositions which are surprisingly stable under ordinary storage conditions for prolonged periods of time, e.g. up to six months or longer. The stability of the available chlorine containing compositions of the present invention is unexepected in view of the fact that such compositions would normally be expected to lose available chlorine in the presence of moisture such as water of hydration. As will be evident hereinafter the compositions of this invention comprise a mixture of two species of solid particles, one species comprising a mixture of the phosphate and silicate ingredients-the phosphate species-and the other species consisting substantially of' an available chlorine containing compound. Such compositions which contain up to 25% by weight of water in the form of water of hydration in the phosphate and silicate are, suprisingly, quite stable toward loss of available chlorine and can be used in water in dishwashing machines without attacking the metal components potassium tripolyophosphate (K P O tetrasodium, monohydrogen tripolyphosphate (Na HP o trisodium dihydrogen tripolyphosphate (N21 H P O monosodium tetra-ammonium tripolyphosphate tripotassium dihydrogen tripolyphosphate (K H P O and the like, and hydrates thereof. Such tripolyphosphates may be present in the compositions partly in the anhydrous and hydrate form or may be completely hydrated. The alkali metal tripolyphosphate which is preferably present in the compositions of this invention is sodium tripolyphosphate hexahydrate (Na P O -6H O) or mixtures of this hexahydrate and anhydrous sodium tripolyphosphate. The term hydrated alkali metal tripolyphosphate as used herein is intended to mean and to include partially to completely hydra-ted alkali metal tripolyphosphates or mixtures of anhydrous and partially to completely hydrated alkali metal tripolyphosphates. Although partially to completely hydrated alkali metal tripolyphosphates may be used per se in the phosphate species of solid particles they are usually and preferably formed in situ from anhydrous alkali metal tripoly-phosplates. Whether these tripolyphosphates are present in the composition as partially hydrated, or completely hydrated or mixtures of anhydrous or partially or completely hydrated materials will depend for the most part on the amounts of water employed in preparing the phosphate species of solid particles.

Thus, for example, when the phosphate species of solid particles contain by weight of water and 65%, or less, by weight of the preferred sodium tripolypho-sphate all, or substantially all, of the sodium tripolyphosphate in the particles will .be in the form of sodium tripolyphosphate hexahydrate. On the other hand, when such particles contain about 10% by weight of water and 45% or more by weight of sodium tripolyphosphate, the sodium tripolyphosphate in the particles will consist of a mixture of anhydrous sodium tripolyphosphate and sodium tripolyphosphate hexahyd-rate, with the higher quantities of anhydrous sodium tripolyphosphate present in the particles corresponding to the higher percentage of tripolyphosphate employed and lower quantities of Water employed.

Thus, for example, the amount of the above-defined hydrated sodium tripolyphosphate present in a phosphate species of solid particles may vary widely, but is advantageously in the range of from about 45% to 65% by weight based on the Weight of such particles. If less than 45% by weight of the hydrated sodium t-ripolyphosphate is employed, the compositions generally will not cleanse metalware and dinnerware efficiently. If more than 65% by weight of the hydrated sodium tripolyphosphate is employed,'the composition usually has a bulk density below about 0.6 gram per cubic centimeter and is therefore, not entirely suitable for use in automatic dishwashing machines. Moreover, such composition is usually too expensive.

The alkali metal silicate which is present in the phosphate species of solid particles or granules of the composit-ions of this invention may be any of a number of alkali metal silicates such as, for example, sodium, potassium, lithium and rubidium silicates. The sodium and potassium silicates are preferred, and the sodium silicates are particularly preferred. Examples of alkali metal silicates Which may be employed include those alkali metal silicates having an SiO to M 0 ratio of from about 4:1 to about 0.5 :1, Where M is an alkali metal. Such silicates are capable of containing up to about 50% by weight of water in the form of water of hydration. These alkali metal silicates include alkali metal orthosilicates having an Slo to M 0 ratio of 0.5:1 to 4:1 where M is an alkali metal, and alkali metal metasilicates having an SiO to M 0 ratio of 1: 1. However, as noted above, other silicates or mixtures of silicates (e.g. disilicates and tetrasilicates) having an SiO to M 0 ratio of 4:1 to about 0.521 may be employed. Sodium silicates having an SiO to M 0 ratio of from about 3.75:1 to about 1.611 are particularly preferred.

The amount of anhydrous to partially hydrated alkali metal "silicate which may be present in the phosphate species of solid particles may vary considerably and will usually depend upon a number of factors such as the Water content of the alkali metal silicate that is, the degree of hydration or lack thereof in the anhydrous to partially hydrated alkali metal silicate, and the amount and the extent of hydration of the tripolyphosphate present. Thus, by way of example, when the phosphate species .of solid particles contain between about 10% and about 15% by weight of water, as Water of hydration, the

' alkali metal silicate will almost always be in the substantially anhydrous state. When the phosphate species of particles contain above about 15 by weight of water as water of hydration, the alkali metal silicate will usually be partially hydrated. When such particles contain amounts as low as 45% by weight of sodium tripolyphosphate hexahydrate, the alkali metal silicate may contain up to about 15% by weight of water. Generally, the phosphate species of particles in the compositions will contain from about 30% to about 55% by weight of an anhydrous to partially dehydrated alkali metal silicate, and the amount of water of hydration present in the alkali metal silicate will generally depend on the amount of alkali metal silicate present, the particles containing the smaller amounts of alkali metal silicate usually contain the silicates having the greater amount of Water of hydration.

The phosphate species of solid particles may vary considerably with respect to particle shape, particle size and particle size distribution. Generally the particles may be spherically or irregularly shaped particles or granules having a size and/or shape such that about to about of the particles or granules 'will pass through a No. 20 mesh U.S. Standard Screen and from about 90% to about 95% of the particles will be retained on a No. mesh US. Standard Screen. Generally if the particles are larger, that is, the particles have a particle size such that substantially less than 90% of the particles pass through a No. 20 mesh U.S. Standard Screen, the compositions formed will often have a bulk density of less than 0.6 gram per cubic centimeter and usually are not entirely suitable for use in automatic dishwashers. On the other hand if substantial amounts, e.g. more than about 5% to about 10% of the particles pass through a No. 100 mesh US. Standard Screen the final composition will not be homogeneous and free flowing.

The phosphate species solid particles which comprise a mixture of the tripolyphosphate and silicate may also additionally include, when desirable, a minor amount usually from about 0.1% to about 5.0% by weight of an organic surface active agent. Any of a wide variety of surface active agents may be employed including cationic, anionic and nonionic organic detergents. Of these nonionic, anionic, and mixtures of nonionic and anionic detergents are preferred and nonionic detergents are particularly preferred.

Generally, when it is desired to employ an anionic detergent the amount employed will be in the range of from about 0.1% to about 0.5% by weight of the above mixture whether the anionic detergent is used alone or in conjunction with a nonionic detergent. If more than about 0.5% by weight of anionic detergent is employed the composition will, in most instances, exhibit undesirable foaming properties when used in water. On the other hand, if less than about 0.1% by weight of anionic detergent is employed no appreciable advantage (i.e. increase in surfactant activity) results. When used in conjunction with a nonionic detergent the amount of anionic detergent preferably employed is from about 0.1% to about 0.3% by weight based on the weight of the particle. Particularly preferred mixtures contain from about 0.5% to 5.0% by weight, based on the weight of the mixture, of one or more of the nonionic detergents.

Examples of anionic surface active agents or detergents which can be present in the phosphate species of particles include compounds such as sulfated and sulfonated alkyl, aryl and alkyl-aryl hydrocarbons and alkali metal salts thereof, for example, sodium salts of long chain alkyl sulfates, sodium salts of alkyl napthalene sulfonic acids, sodium salts of sulfonated abietene's, sodium salts of alkylbenzene sulfonic acids, particularly those in which the alkyl group contains from 8-24 carbon atoms, sodium salts of sulfonated mineral oils and sodium salts of sulfosuccinic acid esters such as sodium di-octyl sulfosuccinate.

Examples of nonionic surface active agents or detergents include products formed by condensing one or more alkylene oxides of 2 to 4 carbon atoms, such as ethylene or propylene oxide, preferably ethylene oxide alone or with other oxides, with a relatively hydrophobic compound having one or more reactive hydrogen atoms, for example a compound such as a fatty alcohol, fatty acid, sterol, a fatty glyceride, a fatty amine, an aryl amine, polypropylene glycols, a fatty mercaptan, a tall oil, etc. Nonionic surface active agents also include those products produce the corresponding amide. Other typical examples alkyl alcohol amines (such as methanol amine, ethanolamine, propanolamine etc.) witha fatty acid such as lauric acid, palmitic acid, tall oil fatty acid, abietic acid etc. to produce the corrsponding amide. Other typical examples of those categories of the anionic and nonionic surface active agents are described in Surface Active Agents by Schwartz and Perry, Interscience Publishers, New York, in 1949 and in the Journal of American Oil Chemists Society, volume 34, No. 4, pages 170216 (April 1957).

Nonionic detergents which are particularly preferred are characterized in being low foaming and include polymerized lower alkylene oxide nonionic detergents such as for example, polymerized, condensed lower alkylene oxide, preferably condensates of ethylene oxide wit-h a hydrophobic base formed by condensing propylene oxide with propylene glycol or a lower alcohol such as methyl or ethyl alcohol, which detergents are marketed under the name of P-luronics.

The phosphate species of solid particles as hereinbefore described comprise a mixture of a hydrated alkali metal tripolyphosphate, an anhydrous to partially hydrated alkali metal silicate, water (in the form of water of hydration) in the polyphosphate and the silicate and, when desirable, one or more of the above defined surface active agents constitute, as noted hereinbefore, one of the two species of solid particles which are present in the compositions of this invention. The second of the two species of solid particles present in the compositions of this invention is the chlorine species, that is, such solid particles consist substantially of an available chlorine containing compound.

A wide variety of available chlorine containing compounds including inorganic and organic available chlorine containing compounds may be present in the chlorine species of solid particles employed in the compositions of this invention. Inorganic available chlorine containing compounds include, for example, the chlorinated trisodium phosphates, a class of compounds which consist of physico-chemical combinations in unitary crystalline form of trisodium phosphate and sodium hypochlorite. Such compounds are known and are described, along with their methods of preparation, in United States Letters Patent 1,555,474 or 1,965,304. Organic available chlorine containing compounds include N-chlorinated heterocyclic compounds such as N-chlorinated triazines, for example melamine, ammelide, ammeline and cyanuric acid; other N-chlorinated organic compounds include N-ch lorinated alkyl, aryl, and alkaryl sulfonamides, such as N- ch-loro, benzene sulfonamide, N-chl-oro, nit-robenzene sulfonamide, N ch-loro, methyl and ethyl benzene sultfonamides. Of these available chlorine containing compounds the N-ch-lorinated organic compounds, particularly the N-chlorinated triazine compounds are advantageous and the N-chlorinated cyanuric compounds are especially advantageous. Examples of such N-chlorinated cyanuric acids hereinafter called chlorocyanurate compounds, include chlorocyanuric acids such as dichlorocyanuric acid and trichlorocyanuric acid; metal chlorocyanurates such metal salts of dichlorocyanuric acid and particularly alkali metal salts of dichlorocyanuric acid and hydrates thereof. Of these chlorocyanurate compounds dichlorocyanuric acid and anhydrous alkali metal salts of dichlorocyanuric acid are preferred. Anhydrous potassium dichlorocyanuric acid is the more stable of these compounds and is, therefore, particularly preferred.

As noted hereinbefore the solid particles of the avail able chlorine containing compounds which are employed in the compositions of this invention have a particle size such that at least 90% of the particles are retained on a No. 100 mesh U.S. Standard Screen. Such particles may consist of irregularly shaped particles or granules composed of a powdered available chlorine containing compound which has been compacted, and thereafter ground and/or screened to the desired particle size or, in some instances, may consist substantially of crystals of a chlorocyanurate compound having the desired particle size, and which are prepared, for example, directly in the synthesis of such compound.

The particle size and particle size distribution of the chlorine species may vary to some extent and the particles may in some instances be somewhat larger. For example the size and distribution of the particles may be such that 100% of the particles may be retained on a No. 100 mesh or even on a No. mesh U.S. Standard Screen. It has been.found, however, that when a substantial amount of the particles are coarser than about 20 mesh, such particles are often unsuitable and the use of such particles tends to result in a lack of uniformity in the final compositions, probably due to the settling or segregation of the smaller particles of the composition. Such settling may result in a concentration of available chlorine containing compounds in the dispenser of'the automatic dishwashing machine and a corrosive action of the available chlorine compound on the dispenser and adjacent metal parts of the dishwashing machine. Also, and particularly in the case of irregularly shaped particles, if the particles are substantially larger than about 20 mesh, the bulk density is usually less than 0.6 gram per cubic centimeter. Solid particles of available chlorine containing compounds having a particle size and particle size distribution such that at least of the particles will pass through a No. 20 mesh U.S. Standard Screen and at least 90% of the particles will be retained on a No. mesh U.S. Standard Screen will provide, in combination with the phosphate species of particles, stable freeflowing compositions having the desired bulk density, cleansing and sanitizing properties. These compositions may be used in dishwashing machines without damage to the ceramic dinnerware or to the metallic dishwashing machine components.

Potassium dischlorocyanurate, which is the preferred chlorocyanurate species, exists in three distinct crystalline forms, specifically crystalline potassium dichlorocyanurate monohydrate, having an internal and external triclinic symmetry, a crystalline anhydrous potassium dichlorocyanurate having an internal and external monoclinic symmetry and a crystalline anhydrous potassium dichlorocyanurate having an internal monoclinic symmetry and an external triclinic symmetry. The latter compound, which is a pseudomorph of the monohydrate, may be obtained in the crystalline size desired (e.g. at least 90% of the crystals are retained on a No. 100 mesh screen) by dehydrating (usually by heating) crystals of potassium dichlorocyanurate monohydrate which have been grown to the aforementioned desired crystalline size. Although any of the various potassium dicblorocyanurates, in the form of solid particles, may be employed in the compositions of this invention, it has been found especially desirable to employ anhydrous crystalline potassium dichlorocyanurate whose crystals have the hereinabove defined preferred particle size and are further characterized in having an internal monoclinic symmetry and an external triclinic symmetry. This anhydrous crystalline potassium dichlorocyanurate usually has a bulk density of from about 0.85 to 0.95 gram per cubic centimeter and provides compositions of exceptionally good uniformity and stability.

The amount of available chlorine containing compound, preferably a chlorocyanurate compound in the form of solid particles, which may be incorporated in the compositions of this invention may vary to some extent depending upon the particular chlorocyanurate employed, and is usually in the range of from about 0.5% to about 3.0% by Weight, based on the weight of the composition of the chlorocyanurate compound. Generally, when dichlorocyanuric acid or trichlorocyanuric acid is employed in the form of solid particles, the amount of either of these materials is preferably in the range of from about 0.5 to about 1% by Weight based on the weight of the composition. On the other hand when a metal salt of dichlorocyanuric acid is employed the amount may vary in the range of from about 1 to 3% by weight and when an anhydrous crystalline alkali metal salt of dichlorocyanuric acid is employed the amount may vary from about 1% to about 2% by weight based on the weight of the composition.

One advantageous embodiment of the compositions of this invention comprises an intimate mixture of (A) solid particles in which the particles comprise a mixture of (1) hydrated sodium tripolyphosphate, preferably sodium tripolyphosphate hexahydrate, (2) an anhydrous to partially hydrated alkali metal silicate preferably an alkali metal silicate having an S10 to M ratio of from about 4:1 to about 0.5:1 where M is an alkali metal, and (3) from about 0.1% to about 5% by weight of any of the hereinbefore described nonionic detergents. Such particles are characterized in containing from about to about 25% by weight of water in the form of water of hydration in the polyphosphate and the silicate. The compositions comprise an intimate mixture of such particles and from about 0.5% to about 3% by weight based on the weight of the composition, of solid particles of achlorocyanurate compound, preferably dichlorocyanuric acid or an alkali metal salt of dichlorocyanuric acid. The solid particles of the chlorocyanurate compound are characterized in having a particle size such that at least 90% of the chlorocyanurate particles will be retained on a No. 100 mesh U.S. Standard Screen. The above composition is characterized in having a bulk density of at least 0.6, preferably from about 0.75 to about 0.95, gram per cubic centimeter, is water soluble, stable and is elfective when dissolved in water and used in automatic dishwashing machines in cleansing and sanitizing metalware, glassware, and ceramic dinnerware without adversely affecting the dinnerware or the metal components of the automatic dishwashing machines.

A preferred embodiment of a composition of this invention comprises an intimate mixture of (A) solid partihydrated alkali metal silicate.

cles in which the particles comprise a mixture of (1) from about 45% to about 65% by weight of sodium tripolyphosphate hexahydrate, (2) from about 54.9% to about 30% by weight of an anhydrous to partially bydrated sodium silicate having an SiO to Na O ratio of from about 3.75:1 to about 1.6:1, and (3) from about 3% to about 1% by weight of a polymerized, condensed, lower alkylene oxide nonionic detergent. The above particles are characterized in containing from about 15% to about 25 by weight of water in the form of water of hydration in the tripolyphosphate and the silicate, and in having a particle size such that at least of the particles pass through a No. 20 mesh U.S. Standard Screen, and at-least 90% of the particles are retained on a No. mesh U.S. Standard Screen. In this preferred embodiment the compositions comprise a mixture of such particles and from about 1% to about 2% by weight based on the weightof the composition of solid particles of potassium dichlorocyanurate, most preferably solid crystalline particles of anhydrous potassium dichlorocyanurate whose crystals are characterized in having an internal monoclinic symmetry and an external triclinic symmetry. Such compositions are characterized in having a bulk density of from about 0.75 to about 0.95 gram per cubic centimeter, are Water soluble, and are dry and free-flowing, stable against loss of available chlorine and can be effectively used to cleanse and sanitize glassware, metalware and ceramic dinnerware without a corrosive action thereon, and particularly without adversely effecting the color decorative glazes normally found on domestic ceramic dinnerware. Also the above described compositions may be satisfactorily used in commercial and home dishwashing machines without attacking the metal components of such machines.

It is noteworthy that previously known granular compositions in which available chlorine containing compounds are incorporated along with anhydrous inorganic phosphate salts, including sodium tripolyphosphate, in the granules will generally tend to'adversely effect metalware and dinnerware and will also tend to have corrosive action upon metallic components of automatic dishwashing machines.

The compositions of this invention may be advantageously prepared by a process which comprises the steps of mixing (A) solid particles formed by (l) intimately admixing a granular alkali metal tripolyphosphate, an alkali metal silicate and sufficient water to form a homogeneous mass comprising a mixture of (a) an alkali metal tripolyphosphate, (b) an alkali metal silicate, and (c) from about 10% to about 25% by weight of water, (2) forming said mass into solid particles, e.g. the phosphate species of solid particles hereinbefore defined, and (B) from about 0.5% to about 3.0% by weight, based on the Weight of thecomposition of solid particles of an available chlorine containing compound having a particle size such that at least 90% of such solid particles are retained on a No. 100 mesh U.S. Standard Screen. By so proceeding a composition containing the above mentioned quantities of water, in the form of water of hydration, in the alkali metal tripolyphosphate and/ or in the alkali metal silicate is formed.

In the preparation of the phosphate species of solid particles from about 10% to about 25 by weight of Water per se may be added and mixed with the alkali metal tripolyphosphate and alkali metal silicate and under such circumstances these ingredients will initially be in anhydrous form. Alternatively the water may be added in the form of water of hydration in the tripolyphosphate and/ or in the silicate. Stated differently, the phosphate species of solid particles can be prepared by mixing a hydrated alkali metal phosphate and an anhydrous or The phosphate species of solid particles may also be, and are preferably, prepared by dissolving or dispersing the alkali metal silicate in water and adding and mixing this solution to a granular anhydrous alkali metal tripolyphosphate. By so proceeding a homogeneous mass is formed which, depending upon the method of preparation, may be a dry or moist powdered to granular mixture or a solid mass comprising the above described ingredients. For example, when either or both tripolyphosphate and silicate is in hydrated form, that is, contains water in the form of water of hydration, the mass will usually be dry powdered to granular and may be formed into solid particles by conventional methods of compacting and grinding the mass to the desired, hereinafter defined, particle size. However, when, water is added per se or when the alkali metal silicate is dissolved .or dispersed in water the mass as initially formed, is damp and can be readily formed into solid particles by passing the damp mass through a mesh or screen having the desired particle size. The particles then become dry, due to the hydration of the tripolyphosphate and silicate. Alternatively, the moist mass may be permitted to solidify as the tripolyphosphate and silicate become hydrated, forming a solid mass which can thereafter be ground to the desired particle size by grinding equipment and methods well known to those skilled in the art. The solid particles so formed contain from about 10% to about 25% by weight of water in the form of water of hydration and are then intimately admixed with from about 0.5% to about 3.0% by weight based on the weight of the composition with solid particles of a chlorocyanurate compound having a particle size as hereinbefore defined to form the compositions of this invention.

In one advantageous embodiment the process of this invention comprises first forming the phosphate species of particles by intimately mixing granular sodium tripolyphosphate, preferably anhydrous sodium tripolyphosphate, with an aqueous solution of an alkali metal silicate, preferably an aqueous solution of sodium silicate, in amounts sufiicient to form a mass comprising a mixture of from about 45% to about 65% by weight 01 hydrated sodium tripolyphosphate, the balance of the mass consisting substantially of from about 55% to about 35% by weight of an anhydrous to partially hydrated alkali metal silicate having an Slo to M ratio of from about 4:1 to about 0.5:1 where M is an alkali metal and containing from about 10% to about 25% by weight of water in the form of water of hydration in the polyphosphate and in the silicate. The mass so formed is usually a hard solid after hydration of the tripolyphosphate and silicate and may be formed into solid particles having the desired particle size by conventional grinding techniques. Such particles are mixed with solid particles of any of the hereinbefore defined chlorocyanurate compounds to form the compositions of this invention.

If desired, the phosphate species of solid particles may also include from about 0.1% to about 5% of one or more of the hereinbefore defined surface active agents, which is admixed with the tripolyphosphate, silicate and water prior to forming such mixture into solid particles.

In a preferred embodiment the process of this invention comprises first forming the phosphate species of particles by the steps of (1) intimately admixing granular anhydrous sodium tripolyphosphate, a sodium silicate having an SiO to Na O ratio of from about 3.75:1

- to about 1.621, a polymerized lower alkylene oxide nonionic detergent such as, for example, the condensation product of polyoxyethylene and polyoxypropylene (mol. wt. 1750) containing 20% polyoxyethylene units, or the condensation product of an average of about 6 mols of ethylene oxide with 1 mol of dodecylphenol, and water in amounts sufiicient to form a mass comprising a mixture of (a) from about 50% to about 60% by weight of sodium tripolyphosphate hexahydrate, (b) from about 47% to about 39% by weight of a partially hydrated sodium silicate having the SiO to N21 O ratio hereinbefore defined, and (c)-from about 3% to about 1% by weight of the nonionic detergent. The mass so formed is characterized in containing from about 15% to about 25% by weight of water in the form of water of hydration in the tripolyphosphate and in the silicate. The mass is then formed into solid particles by any of the methods hereinbefore described. The particles are then mixed with about 1% to about 2% by weight, based on the weight of the composition, with solid particles of potassium dichlorocyanurate having a particle size as hereinbefore defined to form the compositions of this invention.

In the preferred process it is important that the Water in the phosphate species of solid particles be in the form of water of hydration prior to admixing such solid particles with the chlorine species of solid particles prefer'ably a chlorocyanurate compound. This can usually be accomplished by ageing the phosphate species for a limited period of time, e.g. from about 20 to 40 minutes,

, prior to or after it has been formed into solid particles.

Normally the alkali metal tripolyphosphates will hydrate rapidly and preferentially and when the silicate is in the anhydrous form in the solid particles the ageing time is usually from about 20 to 30 minutes. However, the silicates in the solid particles tend to hydrate after the hydration of the alkali metal tripolyphosphate, and thus hydrate more slowly. Consequently, longer ageing times, e.g. about 30 to 40 minutes, are required when the conditions are such that. the alkali metal silicate is hydrate-d.

A further understanding of the compositions and processes of this invention will be obtained from the following specific examples which are intended to illustrate the invention but not to limit the scope thereof, parts and percentages being by weight unless otherwise indicated.

EXAMPLE I Mixtures containing the following ingredients in the percentages given in Table I were prepared by homogeneously blending anhydrous sodium tripolyphosphate,

the sodium silicate or silicates and water as hereinafter described.

Table I Ingredient Mixture number Anhydrous sodium tripolyphosphate Sodium tripolyphosphate hexahydrate Sodium metasilicate (anhydrous) SiOzzNfizO Sodium orthosilicate (anhydrous) Si02:Na O= Sodium metasilieate (hydrated) SiO zNa O =4:1

Sodium orthosilieate (hydrated) SiOyNazO =0.5:1

N ouionic detergent A 1 Nonionic detergent B 2 Sodium dodecylbenzene sulfonate Water (as water of hydration) l Condensation product of polyoxyethylene and polyoxypropylene (mol wt. 1,750) containing 20% 2 Condensation product of polyoxyethyleue units.

an average of about 6 mols of ethylene oxide with 1 mol of dodecylphenol.

The above mixtures were prepared by dissolving the sodium silicates in the appropriate amount of water and adding the resultant sodium silicate solutions to granular anhydrous sodium tripolyphosphate. A wet mass was formed in each instance and such wet mass was immediately brushed through a No. mesh US. Standard Screen to form solid particles, and aged for minutes. The resultant products consisted of dense granules having bulk densities of from 0.68 to 0.92 gram per cubic centimeter.

Similar mixtures were prepared in which the material was aged for 40 minutes without being brushed through a 20 mesh screen. The aged material was then ground in a laboratory mill and passed through a 20 mesh screen as -it was being ground. The products obtained by this procedure were substantially the same as the products obtained by the procedure described in the preceding paragraph.

Solid particles of the mixtures containing the ingredients shown in Table I were mixed with solid particles of various chlorocyanurate compounds to produce homogeneous compositions set forth'in Table II.

Table II Table III Available chlorine (percent) Composition No.

Initial 4 days 11 days 0. 42 0. 41 0. 40 0. 71 0. G9 0. 71 1. 83 1. 8O 1. 79 1. l8 1. 17 l. 18 0. 89 0. 89 0. 89 0. 42 0. 40 0. 39 0. 7l 0. 0. 70 1. 20 l. 18 1. l8 0. (i0 0. 59 0. (i0 1. 18 1. 18 1. l8

Compositions 1 through 10 did not lose substantial quantities of available chlorine. However, compositions similar to Compositions 1 through 10 except that the ingredients were intimately mixed as powders and were in the powdered form lost from 10% to 20% available Ingredient (solid particles) Composition Number Mixture No. 1 Mixture No. 2

Mixture N0. 3

Mixture N0. 4... Mixture No. 5.-. Mixture No. 6 Mixture N o. 7 Mixture N 0. 8. Mixture N0. 9. Mixture N o. 10 Trichlorocyanurie acid. Diehlorocyanuric acid Sodium dichlorocyanurate 8. 0 Potassium diehlorocyanurate 1 2.0 Bulk Density 0.75 0.70 0.80 0.95 Partiele}Percent through no. 20 mesh. 100. 0 98 96. 0 98 Size Percent on no. 100 mesh 91. 5 96 92. O 93 Crystalline anhydrous potassium diehlorocyanurate, having an internal monoclinic symmetry and an external trielinie symmetry.

In all instances the solid particles of the chl-orocyanurate compounds present in the compositions had a particle size such that substantially all of the particles passed through a No. 20 mesh US. Standard Screen and more than 90% of the particles were retained on a .No.'100 mesh US. Standard Screen. The trichlorocyanuric acid, dichlorocyanuric acid and sodium dichlorocyanurate were originally powdered materials which had been compacted, that is compressed into a solid mass, ground and screened to obtain the proper particle size. The anhydrous potassium dichlorocyanur-ate consisted of crystals having an hexagonal appearance, which crystals had the above described particle size range and were prepared directly by synthesis of the compound.

EXAMPLE II Five gram quantities of Compositions 1 through 10 were placed in separate glass jars and evaluated for stability againstloss of available chlorine. The jars containing the compositions were placed in an oven at a relative humidity of 90% and a temperature of 60 C. F.) for 11 days. Available chlorine analyses of the compositions were made at the end of the 4th and 11th day and the available chlorine content of each com position was initially determined. The results are shown in Table III.

chlorine when stored undersimilar conditions. These last mentioned compositions consisted of mixtures in which hydrated sodium tripolyphosphat and sodium silicate were employed.

EXAMPLE III Compositions 1 through 10 of Example I were separately evaluated in an automatic dishwashing machine using glassware, metalware and ceramic dishware which had been soiled with a standard soil.

In all instances the compositions effectively cleansed the soiled articles and in no instance was there evidence of a dulling of the glazes on the ceramic ware, corrosion of the metalware or metal components in the automatic dishwashing machines. Compositions containing iden tical ingredients but which were prepared by admixing the ingredients in anhydrous form and without water were similarly evaluated. These anhydrous compositions dulled the glaze of some of the pieces of ceramic dinnerware and there was evidence of corrosion on the metal parts of the automatic washing machine.

The novel compositions of this invention prepared by the processes herein described fulfill a long sought need in that they effectively cleanse articles without damage to the articles or to the automatic dishwashing machines in which they are employed.

What is claimed is:

1. A process for preparing a stable, free-flowing dishwashing composition for machine dishwashers characterized in having a bulk density of at least 0.6 gram per cubic centimeter which comprises the steps of homogeneously mixing together (A) solid particles formed by 1) intimately admixing granular alkali metal tripolyphosphate, an alkali metal silicate having a SiOg to alkali metal oxide mol ratio of from about 4:1 to about 0.5:1, from about 0.1 to about 5.0% by weight, based on the weight of the mixture, of a non-soap synthetic organic detergent selected from the group consisting of non-soap synthetic anionic surface active agents and non-soap synthetic nonionic surface active agents, and suflicient water to form a homogeneous mass consisting essentially of a mixture of (a) from about 45% to about 65% of hydrated alkali metal tripolyphosphate, (b) from about 55% to about 30% of an alkali metal silicate having the aforementioned SiO to alkali metal oxide mol ratio and selected from the group consisting of anhydrous alkali metal silicate, partially hydrated alkali metal silicate and mixtures thereof, (c) from about 0.1% to about 5% by weight of a non-soap synthetic organic detergent selected from the group consisting of non-soap synthetic organic anionic detergents and'non-soap synthetic organic nonionic detergents, and (d) from about to about 25% by weight of water in the form of Water of hydration in said tripolyphosphate and said silicate, and (2) forming said mass into solid particles, and (B) solid particles of from about 0.5 to about 3.0% by weight of the composition of an available chlorine-containing compound selected from the group consisting of chlorinated trisodium phosphates and organic available chlorine-containing compounds and having a particle size such that at least 90% of the last mentioned solid particles are retained on a No. 100 mesh U.S. Standard Screen thereby forming said composition.

'2. A process as in claim 1, wherein said first mentioned alkali metal tripolyphosphate is a granular, anhydrous sodium-tripolyphosphate and said available chlorine-containing compound is an alkali metal dichloroisocyanurate.

3. A process for preparing a stable, free-flowing dishwashing composition for machine dishwashers characterized in having a bulk density of at least 0.6 gram per cubic centimeter which comprises the steps of (A) intimately mixing granular sodium tripolyphosphate, sodium silicate, and water in amounts sufiicient to form a mass 10% to about 25% by weight of water in the form of water of hydration in said polyphosphate and said silicate, (B) aging said mass for a period of from about 20 to about 40 minutes and (C) grinding said mass into solid particles, (D) mixing the said solid particles so formed with from about 0.5% to about 3.0% by Weight, based on the weight of the composition, with solid particles of an available chlorine-containing chlorocyanurate compound having a particle size such that at least of the last mentioned particles are retained on a No. 100 mesh U.S. Standard Screen thereby forming said composition.

4. A-process for preparing a stable, dry, free-flowing composition characterized in having a bulk density of from about 0.75 to about 0.95 gram per cubic centimeter which comprises the steps of (A) intimately admixing granular anhydrous sodium tripolyphosphate, a sodium silicate having an SiO to Na O ratio of from about 3.75:1 to about 1.6:1, a polymerized, lower alkylene oxide nonionic detergent and water in amounts sutficient to form a mass comprising a mixture of (1) from about 50% to about 60% by weight of sodium tripolyphosphate hexahydrate, (2) from about 47% to about 39% by weight of a partially hydrated sodium silicate having said SiO to Na 0 ratio, (3) from about 3% to about 1% by weight of said nonionic detergent which is condensation product of polyoxyethylene and polyoxypropylene containing 20% polyoxyethylene units, said mass being further characterized in containing from about 15% to about 25% by weight of water in the form of water of hydration in said tripolyphosphate and said silicate, (B) forming said-mass into solid particles having a particle size such that at least of the particles pass through a No. 20 mesh U.S. Standard Screen and are retained on a No. mesh U.S. Standard Screen, (C) mixing the solid particles so formed with from about 1% to about 2% by weight, based on the Weight of the composition, of solid particles of potassium dichlorocyanurate having a particle size such that at least 90% of said last mentioned particles are retained on a No. 100 mesh U.S. Standard Screen, thereby forming said composition.

References Cited by the Examiner UNITED STATES PATENTS 2,874,123 2/1959 Schaafsma et al. 252 XR 2,895,916 7/1959 Milenkevich et al. 25299 2,952,638 9/ 1960 Davis 252137 XR 2,980,622 4/1961 Symes 25299 3,002,931 10/1961 Symes 25299 3,035,054 5/1962 Symes et a1 25299 XR 3,093,590 6/1963 Ferris 25299 3,112,274 11/ 1963 Morgenthaler et a1. 25299 FOREIGN PATENTS 647,241 8/ 1962 Canada;

JULIUS GREENWALD, Primary Examiner. 

1. A PROCESS FOR PREPARING A STABLE, FREE-FLOWING DISHWASHING COMPOSITION FOR MACHINE DISHWASHERS CHARACTERIZED IN HAVING A BULK DENSITY OF AT LEAST 0.6 GRAM PER CUBIC CENTIMETER WHICH COMPRISES THE STEPS OF HOMOGENEOUSLY MIXING TOGETHER (A) SOLID PARTICLES FORMED BY (1) INTIMATELY ADMIXING GRANULAR ALKALI METAL TRIPOLYPHOSPHATE, AN ALKALI METAL SILICATE HAVING A SIO2 TO ALKALI METAL OXIDE MOL RATIO OF FROM ABOUT 4:1 TO ABOUT 0.5:1, FROM ABOUT 0.1 TO ABOUT 5.0% BY WEIGHT, BASED ON THE WEIGHT OF THE MIXTURE, OF A NON-SOAP SYNTHETIC ORGANIC DETERGENT SELECTED FROM THE GROUP CONSISTING OF NON-SOAP SYNTHETIC ANIONIC SURFACE ACTIVE AGENTS AND NON-SOAP SYNTHETIC NONIONIC SURFACE ACTIVE AGENTS, AND SUFFICIENT WATER TO FORM A HOMOGENEOUS MASS CONSISTING ESSENTIALLY OF A MIXTURE OF (A) FROM ABOUT 45% TO ABOUT 65% OF HYDRATED ALKALI METAL TRIPOLYPHOSPHATE, (B) FROM ABOUT 55% TO ABOUT 30% OF AN ALKALI METAL SILICATE HAVING THE AFOREMENTIONED SIO2 TO ALKALI METAL OXIDE MOL RATIO AND SELECTED FROM THE GROUP CONSISTING OF ANHYDROUS ALKALI METAL SILICATE, PARTIALLY HYDRATED ALKALI METAL SILICATE AND MIXTURES THEREOF, (C) FROM ABOUT 0.1, TO ABOUT 5% BY WEIGHT OF A NON-SOAP SYNTHETIC ORGANIC DETERGENT SELECTED FROM THE GROUP CONSISTING OF NON-SOAP SYNTHETIC ORGANIC ANIONIC DETERGENTS AND NON-SOAP SYNTHETIC ORGANIC NONIONIC DETERGENTS, AND (D) FROM ABOUT 10% TO ABOUT 25% BY WEIGHT OF WATER IN THE FORM OF WATER OF HYDRATION IN SAID TRIPOLYPHOSPHATE AND SAID SILICATE, AND (2) FORMING SAID MASS INTO SOLID PARTICLES, AND (B) SOLID PARTICLES OF FROM ABOUT 0.5 TO ABOUT 3.0% BY WEIGHT OF THE COMPOSITION OF AN AVALIABLE CHLORINE-CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF CHLORINATED TRISODIUM PHOSPHATES AND ORGANIC AVAILABLE CHLORINE-CONTAINING COMPOUNDS AND HAVING A PARTICLE SIZE SUCH THAT AT LEAST 90% OF THE LAST MENTIONED SOLID PARTICLES ARE RETAINED ON A NO. 100 MESH U.S. STANDARD SCREEN THEREBY FORMING SAID COMPOSITION. 